Sure! Venturing into Sendai, Matsushima, and Tsuruoka in Japan is a splendid choice. Here are some tips for you:

Best Time to Visit:
For Sendai and Matsushima, the best season would be spring (late March to May) when cherry blossoms are in full bloom or autumn (October to November) when the leaves change color. For Tsuruoka, the best time to visit is from late April to early November when various festivals, including the Tsuruoka Hachimangu Shrine Festival, are held.

Route and Accessibility:
You can easily access these cities by Shinkansen (bullet train), car, and by air.
In Sendai, the city's subway system, buses, or rental bicycles are convenient for sightseeing. Matsushima can be explored by foot, listed as one of Japan's three most scenic sights. Tsuruoka's attractions are best reached by car or by bus.

Altitude and Acclimatization:
These three cities are located near sea level, so acclimatization is not a problem. However, if you decide to hike up the mountains, take time to acclimatize to avoid health issues.

Accommodation and Booking:
You should book your accommodation in advance, especially if you are visiting during the popular spring and autumn seasons. A variety of options such as hotels, traditional ryokans (Japanese inns), and affordable guesthouses are available.

Clothing and Essentials:
Carry clothing according to the season. In summers, carry light cotton clothes, and in winters, heavy woolens. Comfortable, walking shoes are a must for sightseeing. Definitely carry a good camera, as the scenery is spectacular.

Health and Safety:
Japan is quite safe and clean but always follow basic precautions. Check the local weather forecasts during your travel, as Japan is prone to natural disasters like typhoons and earthquakes.

Local Etiquette and Respect:
Japanese culture values respect for others. Use polite phrases, bow when greeting others, avoid loud conversations in public, and respect local customs and traditions.

Lastly, samplings of the local culinary delights in these three locales - Gyutan in Sendai, seafood in Matsushima and shonai cuisine in Tsuruoka - are an absolute must. Enjoy your trip!